Chapter 8: Web Server Hardware and Software

1. Chapter 8:Web Server Hardware and Software

2. Web Server Basics • The main job of a Web server computer is to respond to requests from Web client computers • Three main elements of a Web server: • Hardware • Operating system software • Web server software

3. Types of Web Sites Development sites Used to evaluate different Web designs Intranets Corporate networks that house internal memos, corporate policy handbooks, and a variety of other corporate documents Extranets Intranets that allow authorized parties outside the company to access information stored in the system Transaction-processing sites Commerce sites that must be available 24 hours a day, seven days a week Content-delivery sites Deliver content such as news, histories, summaries, and other digital information

4. Web Clients and Web Servers • Client/server architectures • Client computers typically request services • A server processes the clients’ requests • Web software • Lets different types of computers running different operating systems communicate

5. Client Server Architecture and Software

6. Dynamic Content Dynamic content is nonstatic information constructed in response to a Web client’s request Dynamic page Web page whose content is shaped by a program in response to user requests Static page An unchanging page retrieved from disk Server-side scripting Programs running on a Web server create Web pages before sending them back to the requesting Web clients Dynamic page-generation technologies include: Active Server Pages (ASP) JavaServer Pages (JSP) PHP: Hypertext Preprocessor (PHP)

7. Various Meanings of “Server” • Server • Computer used to provide files or make programs available to other computers • Server software • Used by a server computer to make files and programs available to other computers • Database server • Server computer on which database management software runs

8. Server Architecture • Two-tier architecture A web server responds to requests for web pages and a database server provides backend data storage • Multi-tier architecture A web server is linked to a middle-tier layer that typically includes a series of application servers that perform specific tasks, as well as to a backend layer of existing corporate systems

9. Two-Tier Client/Server Architecture Two-tier client/server architecture has only one client and one server Request message Message that a Web client sends to request a file or files from a Web server Typical request message contains: Request line Optional request headers Optional entity body Request line Contains a command, the name of the target resource, and the protocol name and version number Request headers Can contain information about types of files that the client will accept in response to a request Entity body Used to pass bulk information to the server

11. Three-Tier and N-Tier Client/Server Architectures

12. Web Application Servers • Software programs that provide the specific business functionality required of a web site. Include: • Catalog display • Transaction processing • Audio/video server • Auction server • B2B server APACHE has 62% of the market of Web server software Exercise: For more information, go to: www.apache.org

13. Right-sizing Your Hardware Platform: The Supply Side • Scalability: the ability of a site to increase in size as demand warrants • Scale hardware vertically or horizontally • Improve processing architecture of the site

14. Vertically and Horizontally Scaling a System

15. Software for Web Servers Operating system tasks include running programs and allocating computer resources Linux Open-source operating system that is easy to install, fast, and efficient Open-source software Developed by a community of programmers who make it available for download at no cost The most popular Web server programs are: Apache HTTP Server Microsoft Internet Information Server (IIS) Sun Java System Web Server (JSWS) Netcraft A networking consulting company in Bath, England Accumulates popularity rankings Go to www.netcraft.com and check out some data and surveys

16. Solutions to the Spam Problem Reduce the likelihood that a spammer can automatically generate e-mail addresses Control exposure of an e-mail address Use multiple e-mail addresses Content filtering strategy Require software that identifies content elements that indicate if a message is (or is not) spam Content-filtering techniques Black list spam filter Looks for known spammer From addresses in incoming messages White list spam filter Examines From addresses and compares them to a list of known good sender addresses Challenge-response technique Compares all incoming messages to a white list

17. Indexing and Searching Utility Programs • Search engines or search tools • Search either a specific site or the entire Web for requested documents • Indexing program • Can provide full-text indexing that generates an index for all documents stored on a server • Can often index documents stored in many different file formats

18. Data Analysis Software • Web servers can capture: • Data about who is visiting a Web site • How long the visitor’s Web browser viewed the site • Date and time of each visit • Which pages a visitor viewed • Data captured by Web servers are stored in a log file

19. Web Server Performance Evaluation • Benchmarking • Testing used to compare the performance of hardware and software • Throughput • Number of HTTP requests that a hardware and software combination can process in a unit of time • Response time • Time required by a server to process one request

20. Load-Balancing Systems • Load-balancing switch • Piece of network hardware that monitors the workloads of servers attached to it • Assigns incoming Web traffic to a server that has the most available capacity at that instant in time